One approach to shrinking complex electronic circuits envisions joining DNA-organic molecule-DNA (DOD) building blocks into arrays. Stanford University scientists have now demonstrated a method to attach DNA to a surface and to control the orientation and stretching of the DNA such that DOD building blocks could be used to build circuits. From nanotechweb.org, written by Belle Dumé, “Tethering and stretching DNA” (requires free registration):

Researchers at Stanford University in the US have developed a reproducible surface chemistry technique for tethering DNA molecules onto surfaces and a new way to stretch the molecules to various lengths. The method could be used to make large-scale nanoelectronic devices based on single organic molecules.

Scientists recently discovered that DNA can be used as a molecular scaffold to make metal contacts to organic semiconductors. A key step in this process involves being able to tether the DNA to various surfaces and stretch the molecule to varying lengths.

Zhenan Bao and colleagues’ new strategy involves synthesizing hybrid DNA-organic molecule-DNA (DOD) structures, then stretching and tethering the DOD assemblies between two microscopic metal electrodes. The researchers then make metal electrode-organic molecule-metal electrode (MOM) structures by further metallizing the DNA segments within the DOD structures.

The team then exploited so-called biotin-Streptavidin linkage chemistry to tether the DNA assemblies to device surfaces (quartz in this case). The basic steps are as follows: functionalizing the surface with amine (-NH2) terminated silanes; reacting the amines with N-hydroxysuccinimide (NHS) functionaliszed polyethylene glycol (PEG) chains terminated with biotin; and using Streptavidin to create a link to biotin-terminated DNA molecules. …

The research was published in ACS Nano (abstract), and is currently available without subscription.

Although this is a promising bottom-up approach to nanoscale integration of single organic molecules, this is not yet a way to build atomically precise circuits because the surface attachment points can not be defined to atomic precision and the DNA molecules are several micrometers long. The advantages of using single molecule semiconductors fade if the precision of surface attachment and the length of the connectors can not be reduced to comparable dimensions. It remains to be seen how far the researchers get in “developing in situ DNA metallization for ultimately enabling efficient fabrication of large-scale nanoelectronic devices based on single organic molecules.”